Laboratory data of dog rabies in southern Cameroon from 2010 to 2013
© Sadeuh-Mba et al.; licensee BioMed Central. 2014
Received: 14 April 2014
Accepted: 18 November 2014
Published: 12 December 2014
Dog rabies is endemic in most African countries and the risk of human rabies is estimated to be high in Cameroon according to WHO estimations in 2010. This study aimed to describe the circulation rabies virus (RABV) among dogs in the southern regions of Cameroon from 2010 to 2013 in a context, where mass vaccination campaigns are launched annually in order to control rabies in domestic animals including dogs and cats.
From 2010 to 2013, 93 animal specimens (dogs: 91, monkey: 1, pig: 1) originating from the southern regions of Cameroon were collected and tested for rabies virus at the Centre Pasteur of Cameroon by fluorescent antibody test (FAT) and virus isolation. Of the total dog specimens, 69.2% (63/91) originated from the central part of the southern regions and 50.5% (46/91) were from the capital city Yaounde. Overall, 74.2% (66/89) of dogs’ specimens that could be tested were found rabies-positive while specimens from the monkey and pig were tested negative. Overall, dog rabies was repeatedly detected in the southern regions of Cameroon especially in the nation capital, Yaounde even though low specimen submission and geographic bias did not permit major conclusions about its actual rate, geographical and over time distribution.
The results of this study indicate that rabies is endemic in the dog population which is of public health concern. Therefore, coordinated rabies control program should be conducted to reduce the rabies incidence in dogs and in humans. In addition, proper rabies surveillance program including reporting system should be established to monitor the success of the control program in Cameroon.
Rabies is a viral zoonotic infection commonly caused by the rabies virus (RABV), but also by other negative strand RNA viruses belonging to the Lyssavirus genus in the Rhabdoviridae family [1, 2]. RABV is transmitted to healthy mammals through the exposure to the saliva of infected mammals of the same or a different species mainly through bite or scratch. Rabies surveillance and control programs based on effective vaccination and dog population management have led to the elimination of rabies in domestic animals in Western Europe, North America as well as in some countries in Asia. However, rabies remains a public health issue in developing countries where dogs remain the main reservoir and vector of disease transmission to humans [3–5]. It is estimated that about 55,000 human deaths annually are caused by rabies infection worldwide and 44% occur in Africa [3, 5].
Specimens and methods
Animal specimens were collected with the approval of the Cameroonian Ministry of Livestock Fisheries and Animal Industries within the framework of the rabies diagnosis in Cameroon. Specimens analyzed were obtained by convenience sampling since there is no system in place to actively collect animal specimens from the veterinary networks for rabies diagnosis in Cameroon. Thus, passive surveillance during 2010–2013 was maintained by veterinarians and animal health officers who sent specimens from animals that expressed rabies symptoms, appeared sick and/or had bitten someone, for rabies testing at CPC. The entire head of the suspected animals were sent frozen to CPC where the brain was extracted, kept at +4°C and tested within 48 h.
Detection of rabies nucleocapsid was performed on the brain postmortem biopsy by fluorescent antibody test (FAT) using rabbit IgG against RABV nucleocapsid (Bio-Rad, Marnes-la Coquette, France) as previously described . The negative FAT results were further confirmed by virus isolation which was performed by inoculation into Murina neuroblastoma cell cultures as described elsewhere .
Geographic origin of the specimens
Rabies laboratory diagnosis in domestic animals, Cameroon, 2010–2013
Tested positive (%)
Geographic and overtime distribution of positive samples
The percentage of rabies-infected dogs over the 2010–2013 period (74.2%; 66/89) was apparently higher than the one reported during the 1990–1999 period (45.8%; 330/721) . The higher frequency in this study may be due to the fact that most specimens were sampled in Yaounde and where thus sent to the laboratory in good conditions. This difference may also be due to more accurate clinical diagnosis by veterinarians/and technicians in the field. As previously reported in Cameroon , dog rabies seemed to be more frequent in the urban areas than rural areas. However, this observation could be a result of a bias caused by the poor accessibility to the diagnostic laboratory at CPC and also the lack of knowledge of the rural population about dog rabies. There is a need of increased sensitization of the population, especially in rural areas, about the rabies risk. Another factor that may have account for underestimation of dog rabies in rural areas is the affordability of sample shipment from periphery levels to the CPC laboratory at the central level. Furthermore, the fact that dog owners have to pay for the treatment of bitten individuals constitutes a factor of underreporting to the local health authorities. As reported in other African countries [5, 8], reporting bias, lack of sample submission from distant regions especially rural areas and the lack of awareness campaigns may have resulted to the underestimation of the overall rate of dog rabies in the southern Cameroon.
Despite the main intervention of animal health authorities through mass vaccination campaigns of dogs and cats against rabies launched regularly on the international rabies day, dog rabies remains a threat to human health in Cameroon. Theses campaigns have not been as effective as expected from previous reports [9, 10]. Till now, interventions for the prevention of human rabies through dog rabies control have been based on very limited data generated from passive surveillance. To be more effective future vaccination campaigns against dog rabies need to be accompanied by a scientific evaluation in the light of data generated from an active rabies surveillance system and further field studies. In particular, these later should address the specific gaps in the knowledge about the awareness of the human populations, dog demography and ecology as well as the optimal timing and periodicity of vaccination campaigns.
Not required. Animal specimens were collected with the approval of the Cameroonian Ministry of Livestock, Fisheries and Animal Industries within the frame of the rabies surveillance in Cameroon.
We thank all field veterinarians/technicians, for specimens’ collection and submission; the laboratory technicians involved in the diagnosis; and Dr. Lea Knopf for the critical review of the manuscript.
We are grateful to the Cameroonian Ministry of Livestock Fisheries and Animal Industries for providing financial support to the laboratory diagnosis of animal rabies at Centre Pasteur du Cameroon since 2012.
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